Use set_solver+ everywhere instead of set_solver-.

theories/lifetime/model/creation.v

theories/lifetime/model/reborrow.v

theories/typing/lib/arc.v

theories/typing/lib/rc/rc.v

theories/typing/lib/rc/weak.v

theories/typing/lib/refcell/ref_code.v

theories/typing/lib/refcell/refcell.v

theories/typing/lib/refcell/refcell_code.v

theories/typing/lib/refcell/refmut_code.v

theories/typing/lib/rwlock/rwlockreadguard_code.v

theories/typing/programs.v